This patent document relates to optical devices and optical sensing techniques including optical gyroscopes and optically sensing rotation.
Sensing of rotation can be used in a wide range of applications, including, e.g., navigation, motion sensing, motion control including object stability control, game console controllers, hand-held devices such as smartphones. Optical gyroscopes can be designed to use rotation-induced changes in the optical interference pattern of two counter-propagating optical beams to measure the rotation. Many optical gyroscopes are based on an optical Sagnac interferometer configuration including various interferometric fiber-optic gyroscopes (IFOGs). Such optical gyroscopes can be designed without moving parts and thus eliminate the wear and tear in other gyroscopes with an oscillating proof mass or a moving component. IFOGs are commercialized and in mass production for various military and civilian applications.
FIGS. 1 and 2 show two examples of optical interferometric gyroscopes based on a Sagnac interferometer. FIG. 1 shows a bulk design and FIG. 2 shows a IFOG design based on a fiber loop. To increase the sensitivity and reliability, a relatively long length of fiber coil (e.g., hundreds to thousands meters of fiber) may be used. FIG. 2 further shows an example of a phase modulation mechanism in the IFOG to bias the gyro at a most sensitive point, and a closed loop circuit that is used to increase IFOG's dynamic range and improve its detection sensitivity.